The present invention is related to computer storage and in particular to backup and recovery of data.
Several methods are conventionally used to prevent the loss of data. Typically, data is backed up in a periodic manner (e.g., once a day) by a system administrator. Many systems are commercially available which provide backup and recovery of data; e.g., Veritas NetBackup, Legato/Networker, and so on. Another technique is known as volume shadowing. This technique produces a mirror image of data onto a secondary storage system as it is being written to the primary storage system.
Journaling is a backup and restore technique commonly used in database systems. An image of the data to be backed up is taken. Then, as changes are made to the data, a journal of the changes is maintained. Recovery of data is accomplished by applying the journal to an appropriate image to recover data at any point in time. Typical database systems, such as Oracle, can perform journaling.
Except for database systems, however, there are no ways to recover data at any point in time. Even for database systems, applying a journal takes time since the procedure includes:
reading the journal data from storage (e.g., disk)
the journal must be analyzed to determine at where in the journal the desired data can be found
apply the journal data to a suitable image of the data to reproduce the activities performed on the data—this usually involves accessing the image, and writing out data as the journal is applied
Recovering data at any point in time addresses the following types of administrative requirements. For example, a typical request might be, “I deleted a file by mistake at around 10:00 am yesterday. I have to recover the file just before it was deleted.”
If the data is not in a database system, this kind of request cannot be conveniently, if at all, serviced. A need therefore exists for processing data in a manner that facilitates recovery of lost data. A need exists for being able to provide data processing that facilitates data recovery in user environments other than in a database application.